Iceweasel, Epiphany, Opera and Dillo!
Iceweasel everyday, Epiphany when on battery etc.
Epiphany, while basic, has some surprising simple features. It works and it's fast.
And Opera always has a place on my computer.

Two
IE7 because Icannot uninstall it. i will update it to IE8 at some point due to security reasons. although rare some websites are still written for IE only... so sometimes it needs to be used.
my main browser is Opera.

btw anyone find it funny that microsoft sites have to be put in compatibility mode list for IE8?

Difficult to say. On Windows, usually 3, IE cause it's there, FF as primary, Opera as secondary, in some cases. On Linux, depending on distro, there can be one or five, but mostly 1-2. So the average is 2, but use just one 99.5543% of time.
Mrk